The impact of greenspace or nature-based interventions on cardiovascular health or cancer-related outcomes: A systematic review of experimental studies

Abstract

Significance: Globally, cardiovascular disease (CVD) and cancer are leading causes of morbidity and mortality. While having different etiologies, CVD and cancer are linked by multiple shared risk factors, the presence of which exacerbate adverse outcomes for individuals with either disease. For both pathologies, factors such as poverty, lack of physical activity (PA), poor dietary intake, and climate change increase risk of adverse outcomes. Prior research has shown that greenspaces and other nature-based interventions (NBIs) contribute to improved health outcomes and climate change resilience.

Objective: To summarize evidence on the impact of greenspaces or NBIs on cardiovascular health and/or cancer-related outcomes and identify knowledge gaps to inform future research.

Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 and Peer Review of Electronic Search Strategies (PRESS) guidelines, we searched five databases: Web of Science, Scopus, Medline, PsycINFO and GreenFile. Two blinded reviewers used Rayyan AI and a predefined criteria for article inclusion and exclusion. The risk of bias was assessed using a modified version of the Newcastle-Ottawa Scale (NOS). This review is registered with PROSPERO, ID # CRD42021231619.

Results & discussion: Of 2565 articles retrieved, 31 articles met the inclusion criteria, and overall had a low risk of bias. 26 articles studied cardiovascular related outcomes and 5 studied cancer-related outcomes. Interventions were coded into 4 categories: forest bathing, green exercise, gardening, and nature viewing. Outcomes included blood pressure (BP), cancer-related quality of life (QoL) and (more infrequently) biomarkers of CVD risk. Descriptions of findings are presented as well as visual presentations of trends across the findings using RAW graphs. Overall studies included have a low risk of bias; and alluvial chart trends indicated that NBIs may have beneficial effects on CVD and cancer-related outcomes.

Conclusions & implications: (1) Clinical implication: Healthcare providers should consider the promotion of nature-based programs to improve health outcomes. (2) Policy implication: There is a need for investment in equitable greenspaces to improve health outcomes and build climate resilient neighborhoods. (3) Research or academic implication: Research partnerships with community-based organizations for a comprehensive study of benefits associated with NBIs should be encouraged to reduce health disparities and ensure intergenerational health equity. There is a need for investigation of the mechanisms by which NBIs impact CVD and exploration of the role of CVD biological markers of inflammation among cancer survivors.

Fig 1. Graphical illustration of PRISMA 2020 guidelines in articles’ selection process.

Fig 2. Impact of greenspace or nature based interventions on CV health outcomes.

The first column represents articles, the second column represents geographical settings of studies, the third column represents specific interventions used in the studies, the fourth column represents the measures of CV health, while the fifth column represents the conclusion in terms of protective effects (Beneficial effect), or no significant results (Not significant). This graphical representation shows an overall trend in findings across all studies included. Acronyms: SBP¹: Systolic blood pressure; DBP²: Diastolic blood pressure; BNP³: Brain natriuretic peptide; HRV⁴: Heart rate variability; RAS⁵: Renin-angiotensin system components; PNSA⁶: Parasympathetic Nervous System Activity; SNSA⁷: Sympathetic Nervous System Activity; hsCRP⁸: High sensitivity C-reactive protein; TNF- α⁹: Tumor necrosis factor alpha; HR¹⁰: Heart rate; MDA¹¹: Malondialdehyde; RAGE¹²: Receptor for advanced glycation end products; iNOS¹³: Inducible nitric oxide synthase; MCP-1¹⁴: Monocyte chemoattractant protein-1; ET-1¹⁵: Endothelin-1; PP¹⁶: Pulse pressure; AdipoQ¹⁷: Adiponectin; Hcy¹⁸: Homocysteine; NADPH¹⁹: NADPH oxidase p47; HDL²⁰: High-density lipoprotein; LDL²¹, and Low-density lipoprotein.

Fig 3. The impact of greenspace or nature based interventions on cancer-related outcomes.

The first column represents articles, the second column represents geographical settings of studies, the third column represents specific interventions used in the studies, the fourth column represents the measures of cancer-related outcomes, while the fifth column represents the conclusion in terms of protective effects (beneficial effect), no significant results (not significant) or control groups had better outcomes than experimental groups (significant in controls).This graphical representation shows an overall trend in findings across studies. Acronyms: PA¹: Physical activity; NK²: Natural killer cells; QoL³: Quality of life; and IL-6⁴: Interleukin-6.

Fig 4. Forest bathing intervention effects on both CV health and cancer-related outcomes: Trends of associations among all statistical tests conducted.

The first column represents outcome measures while the second column represents summary conclusions in terms of protective effects (beneficial effect) or no significant results (not significant). Acronyms: SBP¹: Systolic blood pressure; DBP²: Diastolic blood pressure; BNP³: Brain natriuretic peptide; HRV⁴: Heart rate variability; RAS⁵: Renin-angiotensin system components; PNSA⁶: Parasympathetic Nervous System Activity; SNSA⁷: Sympathetic Nervous System Activity; hsCRP⁸: High sensitivity C-reactive protein, TNF- α⁹: Tumor necrosis factor alpha; and NK¹⁰: Natural killer cells.

Fig 5. Green exercise intervention effects on CV health outcomes: Trends of associations among all statistical tests conducted.

The first column represents outcome measures while the second column represents summary conclusions in terms of protective effects (beneficial effect) or no significant results (not significant). Acronyms: SBP¹: Systolic blood pressure and DBP²: Diastolic blood pressure.

Fig 6. Vegetable gardening intervention effects on outcomes related to CV health and cancer: Trends of associations among all statistical tests conducted.

The first column represents outcome measures while the second column represents summary conclusions in terms of protective effects (beneficial effect), no significant results (not significant) or control groups had better outcomes than experimental groups (significant in controls). Acronyms: PA¹: Physical activity; QoL²: Quality of life; PNSA³: Parasympathetic Nervous System Activity; SNSA⁴: Sympathetic Nervous System Activity; SBP⁵: Systolic blood pressure; DBP⁶: Diastolic blood pressure; HDL⁷: High-density lipoprotein; LDL^8: Low-density lipoprotein; TNF- α⁹: Tumor necrosis factor alpha; RAGE¹⁰: Receptor for advanced glycation end products; iNOS¹¹: Inducible nitric oxide synthase; MCP-1¹²: Monocyte chemoattractant protein-1, and IL-6¹³: Interleukin-6.

Fig 7. Nature viewing intervention effects on CV health outcomes: Trends of associations among all statistical tests conducted.

The first column represents outcome measures while the second column represents summary conclusions in terms of protective effects (beneficial effect) or no significant results (not significant). Acronyms: PNSA¹: Parasympathetic Nervous System Activity; SNSA²: Sympathetic Nervous System Activity; SBP³: Systolic blood pressure and DBP⁴: Diastolic blood pressure.